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Nitrous oxide sinks and emissions in boreal aquatic networks in Québec

Nature Geoscience volume 9, pages 116120 (2016) | Download Citation

Abstract

Inland waters are important sites of nitrogen processing1,2, and represent a significant component of the global budget of nitrous oxide3, a powerful greenhouse gas4. Measurements have focused on nitrogen-rich temperate rivers, with low-nitrogen freshwater systems at high latitudes receiving less attention. Here we measured surface water nitrous oxide partial pressures and calculated fluxes across 321 rivers, lakes and ponds in three boreal regions of Québec, Canada. Fluxes to the atmosphere ranged from −23.1 to 115.7 μmol m−2 d−1, with high variability among ecosystem types, regions and seasons. Surprisingly, over 40% of the systems sampled were under-saturated in nitrous oxide during the summer, and one region’s aquatic network was a net atmospheric sink. Fluxes could not be predicted from the relatively narrow range in nitrogen concentrations, but the aquatic systems acting as sinks tended to have lower pH, higher dissolved organic carbon and lower oxygen concentrations. Given the large variability in observed fluxes, we estimate that high-latitude aquatic networks may emit from −0.07 to 0.20 Tg N2O-N yr−1. The potential of boreal aquatic networks to act as net atmospheric nitrous oxide sinks highlights the extensive uncertainty in our understanding of global freshwater nitrous oxide budgets.

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Acknowledgements

This study was funded by Natural Sciences and Engineering council of Canada (NSERC) Discovery grants to R.M. and P.A.d.G, and by Hydro-Québec, and is part of the research programme of the NSERC/HQ Industrial Research Chair in Carbon Biogeochemistry in Boreal Aquatic Systems (CarBBAS) associated with P.A.d.G. We wish to thank the many field assistants and students from the CarBBAS chair and R.M. research team for providing generous help and valuable scientific insights on the project. We thank Annick St-Pierre and A. Parkes for coordinating, respectively, field sampling and laboratory analysis. We also thank R. Hutchins and A. Heathcote, who performed part of the spatial analysis. This is a contribution to the Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique (GRIL). Data will be made available upon request.

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Affiliations

  1. Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique, Département des Sciences Biologiques, Université de Montréal, C.P. 6128 succ. Centre-ville, Montréal, Québec H3C 3J7, Canada

    • C. Soued
    •  & R. Maranger
  2. Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada

    • P. A. del Giorgio

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Contributions

R.M. and P.A.d.G. conceptualized the study, C.S. and P.A.d.G. conducted the sampling, C.S. performed the analysis, and all authors contributed to the writing.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to R. Maranger.

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DOI

https://doi.org/10.1038/ngeo2611

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